Heat exchangers of the type having a pair of spatially separated headers or manifolds interconnected by a plurality of transverse fluid transfer tubes are well known in the art. Corrugated fins are conventionally inserted between adjacent transverse tubes to facilitate the energy transfer between the fluid flowing through the tubes and an external atmosphere such as air. Heat exchangers, such as taught by Nakajima et al. in U.S. Pat. No. 5,052,478; Granetzke in U.S. Pat. No. 4,960,169; Wallis in U.S. Pat. No. 5,193,613; and Neshina et al. in U.S. Pat. No. 4,825,941 embody unitary headers. These headers are complex and require costly tooling to fabricate and in most instances changes are difficult and relatively expensive to make. In particular, if a change in the pitch (spacing) between the transverse tubes is desired, a whole new set of tooling is generally required. These heat exchanger configurations are not susceptible to making changes without incurring expensive tooling costs. Against this background there arises a need for a heat exchanger design in which the pitch and the number of tubes can readily be changed to accommodate prototype and/or low volume production.